In fact, the evidence suggests the reforms failed to halt a longer standing slide in numeracy. In the case of reading, what reliable information there is shows no sign of improvement. And if there has been a decline, it must have started around the time the national curriculum and testing began.

On the face of it, then, a fundamental aim of the Government’s national curriculum - the raising of basic standards - seems to have failed. No one should take any comfort from this; the real losers are the children involved, not the politicians. But there are a number of lessons to be learned.

The most important may well be that the primary curriculum could be slimmed yet further to concentrate even more on basic skills. Professor Campbell’s evidence pre-dates last year’s slimming down of the national curriculum. But some of the primary heads in our survey feel this has not gone far enough.

Others, including Professor Sig Prais, believe the breadth of the primary maths curriculum has contributed systematically to the decline in pupils’ grasp of arithmetic. He is among those too who argue for approved and carefully researched national curriculum textbooks to ensure that everyone understands what is expected of them, and when.

The sparsity of the available evidence about standards is itself a cause for concern. At the very point the Government should have been interested in tracking what was happening, it closed down its own Assessment of Performance Unit. It is ludicrous that we spend Pounds 34 million a year on testing but that there is not any standardised national assessment of something as fundamental as reading. Perhaps Ministers were under the misapprehension that national curriculum test results would give sensitive enough information on the impact of reform on standards. If so, they now know they were wrong and that the kind of cheap and effective light sampling surveys formerly carried out by the APU need to be started up again.

The failure of the national curriculum so far to achieve such a significant aim ought to serve as a salutary warning to honest politicians of all parties about reforms which depend on professionals who have been ignored, insulted and imposed upon. It is not surprising that disillusioned heads wish politics could be kept out of education. But they do so in vain.

Professionals and politicians are subject to the same forces affecting all public services: the rising aspirations of the consumer (which politicians are inclined to exploit and schools to temper) and the limits on public spending (where the enthusiasms are reversed). What finally brought about government intervention in the curriculum was not that standards were not what they used to be - the evidence suggests they have been broadly just as good or bad for 20 years or more - but that more parents, more employers, more voters were expecting the standards that used to be achieved by a minority.

Heads’ marked enthusiasm for the Liberal Democrat education tax is more wishful thinking: a promise that party will never have to live up to. Meanwhile, schools will look in vain for more money to be thrown at them by any government that is not first convinced that such investment will pay off.

It is encouraging that so many heads in our survey take a positive view of their Office for Standards in Education inspection. The more schools show reluctance to acknowledge the need for improvement, the more they will feel the heavy-handed intervention of politicians and pundits. But headline-catching generalisations about supposed teacher failure can still demoralise the conscientious and deter the best graduates from teaching.

The heads’ support for a national curriculum in teacher training may be welcome. But if there are doubts about the quality of some newly-qualified teachers, simply defining what they should learn will not encourage the most talented to choose a profession perceived as despised and demoralised.